Light-emitting device and method of fabricating the same

ABSTRACT

A light-emitting device having a structure in which a mask used for forming a film such as an organic compound layer does not come in contact with the pixels in forming the light-emitting elements, and a method of fabricating the same. In fabricating the light-emitting device of the active matrix type, a partitioning wall constituted by a second wiring and a separation portion is formed on the interlayer-insulating film, and the pixels are surrounded by the partitioning wall, preventing the mask from coming into direct contact with the pixels, the mask being used for forming the organic compound layer and the opposing electrode of the light-emitting elements.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of fabricating an activematrix-type light-emitting device having a light-emitting element on asubstrate, and to a light-emitting device. The light-emitting elementstands for an element of a structure having an anode, a cathode and anorganic compound layer containing a light-emitting organic material(hereinafter referred to as organic material) that produces EL(electroluminescence) sandwiched therebetween. The light-emittingelement referred to here is also called OLED (organic light-emittingdevice). In this specification, further, a light-emitting panel having alight-emitting element sealed between a substrate and a covering member,and a light-emitting module having an IC mounted on the light-emittingpanel, are generally referred to as light-emitting devices. Theinvention is further concerned with electric appliances using the abovelight-emitting device on the display unit. The EL (electroluminescent)devices referred to in this specification include triplet-based lightemission devices and/or singlet-based light emission devices, forexample.

2. Prior Art

The light-emitting element is highly visible since it emits light byitself, is best suited for decreasing the thickness since it does notuse backlight needed by the liquid crystal display devices (LCDs), andimposes no limitation on the viewing angle. In recent years, therefore,the light-emitting device using the light-emitting element is drawingattention to substitute for the CRTs and LCDs.

The light-emitting element includes a layer containing an organicmaterial that produces EL (electroluminescence: luminescence which isproduced upon the application of a electric field), an anode and acathode. The luminescence produced by the organic material can beclassified into emission of light (fluorescence) of when the singletexcitation state returns back to the ground state and emission of light(phosphorescence) of when the triplet excitation state returns back tothe ground state. The light-emitting device of the present invention mayuse the light-emitting element containing either organic material.

In this specification, the layers provided between the anode and thecathode are all defined as organic compound layers. Concretely speaking,the organic compound layers include a light-emitting layer, a positivehole injection layer, an electron injection layer, a positive holetransporting layer and an electron transporting layer. Basically, thelight-emitting element has a structure in which the anode/light-emittinglayer/cathode are laminated in this order. In addition to thisstructure, the light-emitting element may often have a structure inwhich the anode/positive hole injection layer/light-emittinglayer/cathode are laminated in this order or the anode/positive holeinjection layer/light-emitting layer/electron transporting layer/cathodeare laminated in this order.

In forming the light-emitting element, the layer of the organic compoundis formed by the vaporization method, printing method, ink-jet method orspin-coating method.

Among them, the vaporization method capable of separately applying theorganic compound by using a metal mask or the like mask, is one of thefilm-forming methods frequently used for forming a film of alow-molecular organic material. In forming the active matrix-typelight-emitting element, however, this method arouses a problem in thatthe pixels are damaged when the metal mask comes in contact with thepixels in forming the film of the organic compound, since thelight-emitting elements are formed after the TFTs are formed.

According to the conventional method of fabricating the light-emittingelement as taught in Japanese Patent Laid-Open No. 339968/1999, however,the passivation film is formed after the pixel electrode is formed, andthe organic compound layer and the opposing electrode are formed afterthe passivation film is removed from the pixel electrode portion.Therefore, there has been formed a structure for protection with thepassivation film so that the metal mask will not come in contact withthe pixels. In this specification, the passivation film formed except onthe pixel electrodes is called bank.

By forming the bank prior to forming the layer of the organic compoundand the opposing electrodes as described above, it is allowed to preventthe metal mask from coming into contact with the pixels.

In fabricating the light-emitting element, the bank comprising aninsulating material is formed to surround the pixels after the pixelelectrode is formed for each of the pixels.

The bank works not only to protect the wiring but also to protect thepixel electrodes of the pixels, the organic compound layer and theopposing electrodes from being damaged when they are touched by themetal mask in forming the organic compound layer and the opposingelectrodes by vaporization on the pixel electrodes of the pixels byusing the metal mask, and to prevent the electrodes from beingshort-circuited to the wiring at the time when the opposing electrodesare formed.

However, formation of the bank requires another piece of mask forpatterning.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a method offabricating an active matrix-type light-emitting device without the bankbut which is provided with a function that substitutes for the bank, anda light-emitting device fabricated by this method.

This invention was accomplished in order to solve the above-mentionedproblem, and provides a method of fabricating an active matrix-typelight-emitting device, wherein a structure for protecting thesurroundings of pixels is formed by using an interlayer-insulating filmand a wiring formed on the interlayer-insulating film, in order toprevent a metal mask from coming into direct contact with the pixels informing the light-emitting elements in the pixels.

Formation of the above structure makes it possible to control thepositions for forming the organic compound layer on the pixel electrodesand for forming the film on the opposing electrodes, so that theelectrodes forming the light-emitting elements will not beshort-circuited.

First, a TFT is formed on a substrate. In forming a gate electrode ofthe TFT, there is simultaneously formed a first wiring on a portion ofthe region where the light-emitting element is to be formed to connectthe TFT to a pixel electrode. In this specification, the first wiring iscalled electrode connection wiring. There is, then, formed aninterlayer-insulating film of an insulating material. Upon partlyetching the interlayer-insulating film, the interlayer-insulating filmis also etched from a portion where a pixel is to be formed, and theelectrode connection wiring that has been formed is partly exposed.

Then, a metal film and an insulating film are formed. First, theinsulating film is patterned by dry etching. At this moment, the metalfilm and the insulating film provide sufficiently large selectionratios. Next, the metal film is patterned by wet etching thereby to forma separation portion and a wiring (second wiring) from the insulatingfilm and the metal film. In etching the metal film, the separationportion is simultaneously etched, too. Here, however, the materialforming the second wiring has been so selected as to be etched fasterwith an etching solution than the material forming the separationportion. If the substrate on which the TFT is formed after the secondwiring has been formed, is viewed from the upper side, therefore, thesecond wiring is formed having an area smaller than that of theseparation portion. The etching solution used for the wet etching may bea hydrof luoric acid or a mixed solution containing the hydrof luoricacid, or a mixed solution of phosphoric acid, nitric acid and aceticacid.

The second wiring is so formed as to be electrically connected to thesource or the drain of the TFT. The second wiring is further so formedas to be overlapped on the interlayer-insulating film and on part of theelectrode connection wiring.

The wiring and the separation portion are thus formed on theinterlayer-insulating film. In this specification, the second wiring andthe separation portion formed on the interlayer-insulating film arecalled partitioning walls. In the foregoing was described the case wheredifferent etching methods were used for forming the separation portionand the second wiring, which, however, may be formed by the samewet-etching method. A current control TFT for controlling the amount ofcurrent flowing into the light-emitting element is in contact with theelectrode connection wiring and is electrically connected thereto.

After the partitioning walls have been formed, a pixel electrode isformed for each of the pixels so as to be in contact with the electrodeconnection wiring in a portion that is not overlapped on the secondwiring. The pixel electrode formed here is not in contact with thesecond wiring. An organic compound layer is deposited on the pixelelectrode by the vaporization method by using a metal mask.

Here, the metal mask may be so provided as will not come in contact withthe substrate. Even when the metal mask is brought into contact with thesubstrate, however, the pixels are not damaged. Due to the metal maskand the partitioning wall, it is allowed to form the organic compoundlayer at any desired position maintaining good precision.

Next, an opposing electrode is formed. Here, the electrode is formedwith the partitioning walls as a mask, and is not short-circuited to thepixel electrode or the wiring.

As described above, the bank is formed requiring no mask. Further, thelight-emitting element is not deteriorated with water that is producedat the time when the bank is formed using a resin, and the pixelelectrode is not affected by the temperature at the time when the bankis fired. It is further allowed to form a structure in which the pixelsare surrounded by the interlayer-insulating film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(A) to 1(C) are views illustrating a method of fabricationaccording to this invention;

FIGS. 2(A) to 2(C) are views illustrating a method of fabricationaccording to this invention;

FIGS. 3(A) to 3(C) are views illustrating how to form partitioningwalls;

FIG. 4(A) is an SEM photograph of the partitioning walls;

FIG. 4(B) shows details of a structure shown in the SEM photograph ofFIG. 4(A);

FIG. 5 is a circuit diagram of pixels;

FIG. 6 is a circuit diagram of a pixel;

FIGS. 7(A) to 7(D) are views illustrating the steps of fabrication;

FIGS. 8(A) to 8(C) are views illustrating the steps of fabrication;

FIGS. 9(A) to 9(C) are views illustrating the steps of fabrication;

FIGS. 10(A) and 10(B) are views illustrating a structure for sealing alight-emitting device;

FIG. 11(A) is a view illustrating a pixel unit and a driver;

FIG. 11(B) is a top view illustrating a part of a pixel unit;

FIG. 11(C) is a top view illustrating a part of a pixel unit; and

FIGS. 12(A) to 12(H) are views illustrating examples of electricappliances.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the invention will now be described with reference toFIGS. 1 and 2. FIG. 1(A) illustrates a pixel which is formed in a pluralnumber in a pixel unit.

First, an active layer of Si is formed on a substrate 100. This forms asource region, a drain region and a channel region of the TFT that willbe fabricated later. Here, regions surrounded by dotted lines in FIG.1(A) are called region a (101 a) and region b (101 b). A TFT formed inthe region a (101 a) serves as a switching TFT, and a TFT formed in theregion b (101 b) serves as a current control TFT. That is, an activelayer a (102 a) forms a source region, a drain region and a channelregion of the switching TFT. Further, an active layer b (102 b) forms asource region, a drain region and a channel region of the currentcontrol TFT.

Reference numeral 103 denotes a gate signal line, and a wiring 104connected to the gate signal line forms a gate electrode of theswitching TFT that will be formed later. Described here is a case wherethe device has a double gate structure. The gate structure, however, isin no way limited thereto only but may be a single-gate structure or amultiple-gate structure.

There is further formed, simultaneously with the above wirings, a drainwiring a (105) which is electrically connected to the drain of theswitching TFT. The drain wiring a (105) serves as a gate electrode ofthe current control TFT. There is further formed a current feeder line106 that forms an electric connection to the current control TFT. Thecurrent feeder line 106 feeds an electric current that flows into thelight-emitting element.

Reference numeral 107 denotes an electrode connection wiring thatelectrically connects the current control TFT and the pixel electrodetogether.

After these wirings are formed, an interlayer-insulating film 108 isformed. An insulating material is used for forming theinterlayer-insulating film 108. Concretely speaking, there may be usedan inorganic film containing silicon, such as silicon oxide or siliconnitride, or an organic resin film such as of polyimide, polyamide oracrylic resin.

After the interlayer-insulating film 108 is formed, the region forforming the pixel electrode is patterned into a shape as shown in FIG.1(B). Here, as shown, the interlayer-insulating film has been formed topartly cover the electrode wiring 107.

FIG. 1(C) is a sectional view of a portion along a dotted line AA′ inFIG. 1(B). Namely, in this portion, the wirings are all covered with theinterlayer-insulating film 108.

Next, in addition to a source signal line 109, there are formed a sourcewiring a (110) for electrically connecting the current control TFT tothe current feeder line 106, and a drain wiring b (111) for electricallyconnecting the drain of the current control TFT to the electrodeconnection wiring 107 (FIG. 2(A)).

These wirings are formed by forming the structure shown in FIG. 1(B)and, then, forming a film of a metal material for forming the wirings.The metal material used here may be Al (aluminum) or Ti (titanium), oran alloy of Al and Ti, or an alloy of Al and Si.

On the metal film is further formed a separation film by using amaterial which provides a selection ratio with the etching solution whenit is etched simultaneously with the metal film by the wet-etchingmethod. As described above, the separation film may be formed using anymaterial provided it exhibits a selection ratio to the metal film at thetime of wet etching. Therefore, the separation film may be an inorganicfilm such as of silicon nitride or silicon oxide, or may be a metal filmsuch as of Ti. There may be further used an organic resin such aspolyimide, polyamide, acrylic resin or resist.

A wiring pattern is formed after the metal film and the separation filmare formed. Dry etching is effected after the separation film ispatterned, thereby to form a wiring pattern of the metal film and theseparation film laminated one upon the other. The wiring is wet-etchedto etch the metal film having a larger selection ratio of etching. Whenviewed from the upper side, therefore, the metal film becomes smallerthan the separation film as shown in FIG. 2(A).

Here, a portion along the dotted line AA′ in FIG. 2(A) is patterned,i.e., the metal film is patterned to form a drain wiring b (111). FIG.2(B) is a sectional view of a separation portion 112 formed by etchingthe separation film. In this specification, the separation films formedon the wiring by patterning are all called separation portions. FIG.2(B) illustrates a state where the separation portion 112 is formed onthe drain wiring b (111). In this invention, however, the wirings formedby patterning the separation film all have their upper portions coveredwith the separation portion.

FIG. 2(C) is a sectional view of a portion along a dotted line BB′ inFIG. 2(A). As will be understood from the sectional view of FIG. 2(C),the electrode connection wiring 107 is formed being partly connected tothe drain wiring b (111) and is, hence, electrically connected thereto.

In a region (113) shown in FIG. 2(C), the pixel electrode for formingthe light-emitting element is patterned, and an organic compound layerand an opposing electrode are formed thereon by vaporization by using ametal mask. Here, due to the partitioning wall formed by the drainwiring b (111) and the separation portion 112, it is allowed to preventthe pixel from coming in contact with the metal mask. It is further madepossible to solve the problem of short-circuit between the pixelelectrode and the opposing electrode caused by the positions for formingthe organic compound layer and the opposing electrode.

Further, since the drain wiring b (111) has its upper part completelycovered with the separation portion 112, the problem of short-circuitbetween the drain wiring b (111) and the opposing electrode is preventedat the time when the opposing electrode is formed for forming thelight-emitting element.

Upon putting the invention into practice as described above, the wiringcan be used to substitute for the conventional bank. Therefore, no maskneeds to be used for forming the bank, and the process of fabricationcan be simplified.

Described below are the method of forming the wiring and the separationportion by etching described above, and the shapes thereof.

Referring to FIG. 3(A), a metal film 201 is formed on a substrate 200,and a separation film 202 is formed on the metal film 201. FIG. 3(a) isa sectional view along a dotted line AA′ in FIG. 3(A).

The separation film 202 is patterned by dry etching by using a resist203 to form a separation portion 204 having a desired pattern as shownin FIG. 3(B).

FIG. 3(b) illustrates the sectional structure along a dotted line AA′ inFIG. 3(B).

Here, the metal film 201 is etched by wet etching. At this moment, thematerial forming the separation portion 204 and the material forming themetal film 201 must be those that are capable of providing a sufficientdegree of selection ratio for the etching solution during the etching.

Here, the metal film 201 is etched to form a separation portion 204 anda wiring 205 as shown in FIG. 3(C). FIG. 3(c) shows the sectionalstructure along a dotted line AA′ in FIG. 3(C).

FIG. 4(A) is an SEM photograph of the sectional structures of theseparation portion 204 and the wiring 205 formed by the above method byusing Al as the metal film 201 and SiN as the separation portion 204.

FIG. 4(B) illustrates in detail the structure shown in the SEMphotograph of FIG. 4(A). Reference numerals used here are correspondingto reference numerals used in FIG. 3.

Here, the etching is isotropic in which a thickness (x) of the wiring,an etching distance (y) of the upper part of the wiring in thetransverse direction with the etching center (c) as a reference, and anetching distance (a) of a lower part of the wiring in the transversedirection with the etching center (c) as a reference, satisfy arelationship y=x+α (α>0). In the case of this embodiment, the thicknessx of the wiring is 500 nm, the etching distance a of the lower part ofthe wiring in the transverse direction is 400 nm, and the etchingdistance y of the upper part of the wiring in the transverse directionis 900 nm. Not being limited thereto only according to this invention,further, the wiring material, the width of wiring and the etching ratemay be suitably adjusted such that the above relationship holds true.

EXAMPLES Example 1

This Example deals with the structure of a pixel unit of alight-emitting device fabricated according to this invention.

FIG. 5 is a diagram illustrating, on an enlarged scale, a pixel unit 301of the light-emitting device. The pixel unit 301 is provided with sourcesignal lines (S1 to Sx), current feeder lines (V1 to Vx) and gate signallines (G1 to Gy).

In the case of this Example, a pixel 304 is a region having any one ofthe source signal lines (S1 to Sx), any one of the current feeder lines(V1 to Vx) and any one of the gate signal lines (G1 to Gy). The pixelunit 301 includes plural pixels 304 arranged in the form of a matrix.

Referring to FIG. 6 illustrating the pixel 304 on an enlarged scale,reference numeral 305 denotes a switching TFT. The gate electrode of theswitching TFT 305 is connected to the gate signal line G (G1 to Gx). Theswitching TFT 305 has the source region and the drain region, the one ofwhich being connected to the source signal line S (S1 to Sx) and theother one of which being connected to the gate electrode of a currentcontrol TFT 306 and to a capacitor 308 possessed by each pixel.

The capacitor 308 is for holding the gate voltage (potential differencebetween the gate electrode and the source region) of the current controlTFT 306 when the switching TFT 305 is in the non-selected state (offstate). This Example illustrates the constitution provided with thecapacitor 308. Being not limited to this constitution only, however, theinvention may not be provided with the capacitor 308.

The current control TFT 306 includes the source region and the drainregion, the one of which being connected to the current feeder line V(V1 to Vx) and the other one of which being connected to alight-emitting element 307. The current feeder line V is connected tothe capacitor 308.

The light-emitting element 307 includes an anode, a cathode and anorganic compound layer provided between the anode and the cathode. Whenthe anode is connected to the source region or the drain region of thecurrent control TFT 306, the anode serves as the pixel electrode and thecathode serves as the opposing electrode. Conversely, when the cathodeis connected to the source region or to the drain region of the currentcontrol TFT 306, the cathode serves as the pixel electrode and the anodeserves as the opposing electrode.

An opposing potential is applied to the opposing electrode of thelight-emitting element 307. A power source potential is applied to thecurrent feeder line V. The power source potential and the opposingpotential are given from a power source such as of an IC providedoutside the light-emitting device of the invention.

The switching TFT 305 and the current control TFT 306 may be either then-channel TFTs or the p-channel TFTs. Here, however, when either thesource region or the drain region of the current control TFT 306 isconnected to the anode of the light-emitting element 307, it is desiredthat the current control TFT 306 is the p-channel TFT. Further, wheneither the source region or the drain region of the current control TFT306 is connected to the cathode of the light-emitting element 307, it isdesired that the current control TFT 306 is the n-channel TFT.

Further, the switching TFT 305 and the current control TFT 306 may havea multi-gate structure such as a double-gate structure or a triple-gatestructure instead of the single-gate structure.

Next, described with reference to FIGS. 7 to 9 is a method ofsimultaneously forming, on the same substrate, the pixel unit describedabove and the TFTs (n-channel TFTs and p-channel TFTs) of a drivecircuit provided surrounding the pixel unit.

This Example uses a substrate 900 of a glass such as barium borosilicateglass or aluminoborosilicate glass as represented by the glass #7059 orthe glass #1737 of Corning Co. There is no limitation on the substrate900 provided it has a property of transmitting light, and there may beused a quartz substrate. There may be further used a plastic substratehaving heat resistance capable of withstanding the treatment temperatureof this Example.

Referring next to FIG. 7(A), an underlying film 901 comprising aninsulating film such as silicon oxide film, silicon nitride film orsilicon oxynitride film is formed on the substrate 900. In this Example,the underlying film 901 has a two-layer structure. There, however, maybe employed a structure in which a single layer or two or more layersare laminated on the insulating film. The first layer of the underlyingfilm 901 is a silicon oxynitride film 901 a formed maintaining athickness of from 10 to 200 nm (preferably, from 50 to 100 nm) relyingupon a plasma CVD method by using SiH₄, NH₃ and N₂O as reaction gases.In this Example, the silicon oxynitride film 901 a (having a compositionratio of Si=32%, O=27%, N=24%, H=17%) is formed maintaining a thicknessof 50 nm. The second layer of the underlying film 901 is a siliconoxynitride film 901 b formed maintaining a thickness of from 50 to 200nm (preferably, from 100 to 150 nm) relying upon the plasma CVD methodby using SiH₄ and N₂O as reaction gases. In this Example, the siliconoxynitride film 901 b (having a composition ratio of Si=32%, O=59%,N=7%, H=2%) is formed maintaining a thickness of 100 nm.

Then, semiconductor layers 902 to 905 are formed on the underlying film901. The semiconductor layers 902 to 905 are formed by forming asemiconductor film having an amorphous structure by a known means(sputtering method, LPCVD method or plasma CVD method) followed by aknown crystallization processing (laser crystallizationmethod, heatcrystallization method or heat crystallization method using a catalystsuch as nickel), and patterning the crystalline semiconductor film thusobtained into a desired shape. The semiconductor layers 902 to 905 areformed in a thickness of from 25 to 80 nm (preferably, from 30 to 60nm). Though there is no limitation on the material of the crystallinesemiconductor film, there is preferably used silicon or asilicon-germanium (Si_(x)Ge_(1−x)(X=0.0001 to 0.02)) alloy. In thisExample, the amorphous silicon film is formed maintaining a thickness of55 nm relying on the plasma CVD method and, then, a solution containingnickel is held on the amorphous silicon film. The amorphous silicon filmis dehydrogenated (500° C., one hour), heat-crystallized (550° C., 4hours) and is, further, subjected to the laser annealing to improve thecrystallization, thereby to form a crystalline silicon film. Thecrystalline silicon film is patterned by the photolithographic method toform semiconductor layers 902 to 905.

The semiconductor layers 902 to 905 that have been formed may further bedoped with trace amounts of an impurity element (boron or phosphorus) tocontrol the threshold value of the TFT.

In forming the crystalline semiconductor film by the lasercrystallization method, further, there may be employed an excimer laserof the pulse oscillation type or of the continuously light-emittingtype, a YAG laser or a YVO₄ laser. When these lasers are to be used, itis desired that a laser beam emitted from a laser oscillator is focusedinto a line through an optical system so as to fall on the semiconductorfilm. The conditions for crystallization are suitably selected by aperson who carries out the process. When the excimer laser is used, thepulse oscillation frequency is set to be 300 Hz and the laser energydensity to be from 100 to 400 mJ/cm² (typically, from 200 to 300mJ/cm²). When the YAG laser is used, the pulse oscillation frequency isset to be from 30 to 300 kHz by utilizing the second harmonics and thelaser energy density to be from 300 to 600 mJ/cm² (typically, from 350to 500 mJ/cm²). The whole surface of the substrate is irradiated withthe laser beam focused into a line of a width of 100 to 1000 μm, forExample, 400 μm, and the overlapping ratio of the linear beam at thismoment is set to be 50 to 90%.

Then, a gate-insulating film 906 is formed to cover the semiconductorlayers 902 to 905. The gate-insulating film 906 is formed of aninsulating film containing silicon maintaining a thickness of from 40 to150 nm by the plasma CVD method or the sputtering method. In thisExample, the gate-insulating film is formed of a silicon oxynitride film(composition ratio of Si=32%, O=59%, N=7%, H=2%) maintaining a thicknessof 110 nm by the plasma CVD method. The gate-insulating film is notlimited to the silicon oxynitride film but may have a structure on whichis laminated a single layer or plural layers of an insulating filmcontaining silicon.

When the silicon oxide film is to be formed, TEOS (tetraethylorthosilicate) and O₂ are mixed together by the plasma CVD method, andare reacted together under a reaction pressure of 40 Pa, at a substratetemperature of from 300 to 400° C., at a frequency of 13.56 MHz and adischarge electric power density of from 0.5 to 0.8 W/cm². The thusformed silicon oxide film is, then, heat-annealed at 400 to 500° C.thereby to obtain the gate-insulating film having good properties.

Then, a heat-resistant electrically conducting layer 907 is formed onthe gate-insulating film 906 maintaining a thickness of from 200 to 400nm (preferably, from 250 to 350 nm) to form the gate electrode. Theheat-resistant electrically conducting layer 907 may be formed as asingle layer or may, as required, be formed in a structure of laminatedlayers of plural layers such as two layers or three layers. Theheat-resistant electrically conducting layer contains an elementselected from Ta, Ti and W, or contains an alloy of the above element,or an alloy of a combination of the above elements. The heat-resistantelectrically conducting layer is formed by the sputtering method or theCVD method, and should contain impurities at a decreased concentrationto decrease the resistance and should, particularly, contain oxygen at aconcentration of not higher than 30 ppm. In this Example, the W film isformed maintaining a thickness of 300 nm. The W film may be formed bythe sputtering method by using W as a target, or may be formed by thehot CVD method by using tungsten hexafluoride (WF₆). In either case, itis necessary to decrease the resistance so that it can be used as thegate electrode. It is, therefore, desired that the W film has aresistivity of not larger than 20 μΩcm. The resistance of the W film canbe decreased by coarsening the crystalline particles. When W containsmuch impurity elements such as oxygen, the crystallization is impairedand the resistance increases. When the sputtering method is employed,therefore, a W target having a purity of 99.9999% is used, and the Wfilm is formed while giving a sufficient degree of attention so that theimpurities will not be infiltrated from the gaseous phase during theformation of the film, to realize the resistivity of from 9 to 20 μΩcm.

On the other hand, the Ta film that is used as the heat-resistantelectrically conducting layer 907 can similarly be formed by thesputtering method. The Ta film is formed by using Ar as a sputteringgas. Further, the addition of suitable amounts of Xe and Kr into the gasduring the sputtering makes it possible to relax the internal stress ofthe film that is formed and to prevent the film from being peeled off.The Ta film of a phase has a resistivity of about 20 μΩcm and can beused as the gate electrode but the Ta film of β phase has a resistivityof about 180 μΩcm and is not suited for use as the gate electrode. TheTaN film has a crystalline structure close to the a phase. Therefore, ifthe TaN film is formed under the Ta film, there is easily formed the Tafilm of α-phase. Further, though not diagramed, formation of the siliconfilm doped with phosphorus (P) maintaining a thickness of about 2 toabout 20 nm under the heat-resistant electrically conducting layer 907is effective in fabricating the device. This helps improve the intimateadhesion of the electrically conducting film formed thereon, prevent theoxidation, and prevent trace amounts of alkali metal elements containedin the heat-resistant electrically conducting layer 907 from beingdiffused into the gate-insulating film 906 of the first shape. In anyway, it is desired that the heat-resistant electrically conducting layer907 has a resistivity over a range of from 10 to 50 μΩcm.

Next, a mask 908 is formed by a resist relying upon thephotolithographic technology. Then, a first etching is executed. ThisExample uses an ICP etching device, uses Cl₂ and CF₄ as etching gases,and forms a plasma with RF (13.56 MHz) electric power of 3.2 W/cm² undera pressure of 1 Pa. The RF (13.56 MHz) electric power of 224 mW/cm² issupplied to the side of the substrate (sample stage), too, whereby asubstantially negative self-bias voltage is applied. Under thiscondition, the W film is etched at a rate of about 100 nm/min. The firstetching treatment is effected by estimating the time by which the W filmis just etched relying upon this etching rate, and is conducted for aperiod of time which is 20% longer than the estimated etching time.

The electrically conducting layers 909 to 912 having a first taperedshape are formed by the first etching treatment. The electricallyconducting layers 909 to 912 are tapered at an angle of from 15 to 30°.To execute the etching without leaving residue, over-etching isconducted by increasing the etching time by about 10 to 20%. Theselection ratio of the silicon oxynitride film (gate-insulating film906) to the W film is 2 to 4 (typically, 3). Due to the over-etching,therefore, the surface where the silicon oxynitride film is exposed isetched by about 20 to about 50 nm (FIG. 7(B)).

Then, a first doping treatment is effected to add an impurity element ofa first type of electric conduction to the semiconductor layer. Here, astep is conducted to add an impurity element for imparting the n-type. Amask 908 forming the electrically conducting layer of a first shape isleft, and an impurity element is added by the ion-doping method toimpart the n-type in a self-aligned manner with the electricallyconducting layers 909 to 912 having a first tapered shape as masks. Thedosage is set to be from 1×10¹³ to 5×10¹⁴ atoms/cm² so that the impurityelement for imparting the n-type reaches the underlying semiconductorlayer penetrating through the tapered portion and the gate-insulatingfilm 906 at the ends of the gate electrode, and the acceleration voltageis selected to be from 80 to 160 keV. As the impurity element forimparting the n-type, there is used an element belonging to the Group 15and, typically, phosphorus (P) or arsenic (As). Phosphorus (P) is used,here. Due to the ion-doping method, an impurity element for impartingthe n-type is added to the first impurity regions 914 to 917 over aconcentration range of from 1×10²⁰ to 1×10²¹ atoms/cm³ (FIG. 7(C)).

In this step, the impurities turn down to the lower side of theelectrically conducting layers 909 to 912 of the first shape dependingupon the doping conditions, and it often happens that the first impurityregions 914 to 917 are overlapped on the electrically conducting layers909 to 912 of the first shape.

Next, the second etching treatment is conducted as shown in FIG. 7(D).The etching treatment, too, is conducted by using the ICP etchingdevice, using a mixed gas of CF₄ and Cl₂ as an etching gas, using an RFelectric power of 3.2 W/cm² (13.56 MHz), a bias power of 45 mW/cm²(13.56 MHz) under a pressure of 1.0 Pa. Under this condition, there areformed the electrically conducting layers 918 to 921 of a second shape.The end portions thereof are tapered, and the thicknesses graduallyincrease from the ends toward the inside. The rate of isotropic etchingincreases in proportion to a decrease in the bias voltage applied to theside of the substrate as compared to the first etching treatment, andthe angle of the tapered portions becomes 30 to 60°. The mask 908 isground at the edge by etching to form a mask 922. In the step of FIG.7(D), the surface of the gate-insulating film 906 is etched by about 40nm.

Then, the doping is effected with an impurity element for imparting then-type under the condition of an increased acceleration voltage bydecreasing the dosage to be smaller than that of the first dopingtreatment. For Example, the acceleration voltage is set to be from 70 to120 keV, the dosage is set to be 1×10¹³/cm² thereby to form firstimpurity regions 924 to 927 having an increased impurity concentration,and second impurity regions 928 to 931 that are in contact with thefirst impurity regions 924 to 927. In this step, the impurity may turndown to the lower side of the electrically conducting layers 918 to 921of the second shape, and the second impurity regions 928 to 931 may beoverlapped on the electrically conducting layers 918 to 921 of thesecond shape. The impurity concentration in the second impurity regionsis from 1×10¹⁶ to 1×10¹⁸ atoms/cm³ (FIG. 8(A)).

Referring to FIG. 8(B), impurity regions 933 (933 a, 933 b) and 934 (934a, 934 b) of the conduction type opposite to the one conduction type areformed in the semiconductor layers 902, 905 that form the p-channelTFTs. In this case, too, an impurity element for imparting the p-type isadded using the electrically conducting layers 918, 921 of the secondshape as masks to form impurity regions in a self-aligned manner. Atthis moment, the semiconductor layers 903 and 904 forming the n-channelTFTs are entirely covered for their surfaces by forming a mask 932 of aresist. Here, the impurity regions 933 and 934 are formed by theion-doping method by using diborane (B₂H₆). The impurity element forimparting the p-type is added to the impurity regions 933 and 934 at aconcentration of from 2×10²⁰ to 2×10²¹ atoms/cm³.

If closely considered, however, the impurity regions 933, 934 can bedivided into two regions containing an impurity element that imparts then-type. Third impurity regions 933 a and 934 a contain the impurityelement that imparts the n-type at a concentration of from 1×10²⁰ to1×10²¹ atoms/cm³ and fourth impurity regions 933 b and 934 b contain theimpurity element that imparts the n-type at a concentration of from1×10¹⁷ to 1×10²⁰ atoms/cm³. In the impurity regions 933 b and 934 b,however, the impurity element for imparting the p-type is contained at aconcentration of not smaller than 1×10¹⁹ atoms/cm³ and in the thirdimpurity regions 933 a and 934 a, the impurity element for imparting thep-type is contained at a concentration which is 1.5 to 3 times as highas the concentration of the impurity element for imparting the n-type.Therefore, the third impurity regions work as source regions and drainregions of the p-channel TFTs without arousing any problem.

Referring next to FIG. 8(C), a first interlayer-insulating film 937 isformed on the electrically conducting layers 918 to 921 of the secondshape and on the gate-insulating film 906. The firstinterlayer-insulating film 937 may be formed of a silicon oxide film, asilicon oxynitride film, a silicon nitride film, or a laminated-layerfilm of a combination thereof. In any case, the firstinterlayer-insulating film 937 is formed of an inorganic insulatingmaterial. The first interlayer-insulating film 937 has a thickness of100 to 200 nm. When the silicon oxide film is used as the firstinterlayer-insulating film 937, TEOS and O₂ are mixed together by theplasma CVD method, and are reacted together under a pressure of 40 Pa ata substrate temperature of 300 to 400° C. while discharging the electricpower at a high frequency (13.56 MHz) and at a power density of 0.5 to0.8 W/cm². When the silicon oxynitride film is used as the firstinterlayer-insulating film 937, this silicon oxynitride film may beformed from SiH₄, N₂O and NH₃, or from SiH₄ and N₂O by the plasma CVDmethod. The conditions of formation in this case are a reaction pressureof from 20 to 200 Pa, a substrate temperature of from 300 to 400° C. anda high-frequency (60 MHz) power density of from 0.1 to 1.0 W/cm². As thefirst interlayer-insulating film 937, further, there may be used ahydrogenated silicon oxynitride film formed by using SiH₄, N₂O and H₂.The silicon nitride film, too, can similarly be formed by using SiH₄ andNH₃ by the plasma CVD method.

Then, a step is conducted for activating the impurity elements thatimpart the n-type and the p-type added at their respectiveconcentrations. This step is conducted by thermal annealing method usingan annealing furnace. There can be further employed a laser annealingmethod or a rapid thermal annealing method (RTA method). The thermalannealing method is conducted in a nitrogen atmosphere containing oxygenat a concentration of not higher than 1 ppm and, preferably, not higherthan 0.1 ppm at from 400 to 700° C. and, typically, at from 500 to 600°C. In this Example, the heat treatment is conducted at 550° C. for 4hours. When a plastic substrate having a low heat-resistance temperatureis used as the substrate 501, it is desired to employ the laserannealing method.

Following the step of activation, the atmospheric gas is changed, andthe heat treatment is conducted in an atmosphere containing 3 to 100% ofhydrogen at from 300 to 450° C. for from 1 to 12 hours to hydrogenatethe semiconductor layer. This step is to terminate the dangling bonds of10¹⁶ to 10¹⁸/cm³ in the semiconductor layer with hydrogen that isthermally excited. As another means of hydrogenation, the plasmahydrogenation may be executed (using hydrogen excited with plasma). Inany way, it is desired that the defect density in the semiconductorlayers 902 to 905 is suppressed to be not larger than 10¹⁶/cm³. For thispurpose, hydrogen may be added in an amount of from 0.01 to 0.1 atomic%.

Then, a second interlayer-insulating film 939 of an organic insulatingmaterial is formed maintaining an average thickness of from 1.0 to 2.0μm. As the organic resin material, there can be used polyimide, acrylicresin, polyamide, polyimideamide, BCB (benzocyclobutene) as well asphotosensitive acrylic resin. When there is used, for example, apolyimide of the type that is heat-polymerized after being applied ontothe substrate, the second interlayer-insulating film is formed beingfired in a clean oven at 300° C. When there is used an acrylic resin,there is used the one of the two-can type. Namely, the main material anda curing agent are mixed together, applied onto the whole surface of thesubstrate by using a spinner, pre-heated by using a hot plate at 80° C.for 60 seconds, and are fired at 250° C. for 60 minutes in a clean ovento form the second interlayer-insulating film.

Thus, the second interlayer-insulating film 939 is formed by using anorganic insulating material featuring good and flattened surface.Further, the organic resin material, in general, has a small dielectricconstant and lowers the parasitic capacitance. The organic resinmaterial, however, is hygroscopic and is not suited as a protectionfilm. It is, therefore, desired that the second interlayer-insulatingfilm is used in combination with the silicon oxide film, siliconoxynitride film or silicon nitride film formed as the firstinterlayer-insulating film 937.

Thereafter, the resist mask of a predetermined pattern is formed, andcontact holes are formed in the semiconductor layers to reach theimpurity regions serving as source regions or drain regions. The contactholes are formed by dry etching. In this case, a mixed gas of CF₄, O₂and He is used as the etching gas to, first, etch the secondinterlayer-insulating film 939 of the organic resin material.Thereafter, CF₄ and O₂ are used as the etching gas to etch the firstinterlayer-insulating film 937. In order to further enhance theselection ratio relative to the semiconductor layer, CHF₃ is used as theetching gas to etch the gate-insulating film 906, thereby to form thecontact holes.

Then, a wiring layer 940 formed of an electrically conducting metal filmis formed by sputtering or vacuum vaporization. On the wiring layer 940is further formed a separation layer 941 of a material which provides alarge selection ratio for the wiring layer and for the etching solutionduring the etching. The separation layer 941 may be formed of aninorganic material such as nitride film or oxide film, or may be formedof an organic resin such as polyimide, polyamide or BCB(benzocyclobutene). Or, the separation layer 941 may be formed of ametal material.

Here, the separation layer 941 is patterned by using a mask and is,then, etched to form source wirings 942 a to 945 a, drain wirings 946 ato 948 a and separation portions 942 b to 948 b. In this specification,the structure formed by the separation layer and the wiring is calledpartitioning wall. Further, though not diagramed in this Example, thewiring is formed by a laminate of a 50 nm-thick Ti film and a 500nm-thick alloy film (alloy film of Al and Ti).

Then, a transparent electrically conducting film is formed thereonmaintaining a thickness of 80 to 120 nm, and is patterned to form apixel electrode 949 (FIG. 9(B)). In this Example, the pixel electrode949 works as the anode. Therefore, the pixel electrode 949 is formed byusing an indium oxide-tin (ITO) film or a transparent electricallyconducting film obtained by mixing 2 to 20% of a zinc oxide (ZnO) intoindium oxide.

Further, the pixel electrode 949 is formed being in contact with, andoverlapped on, the contact wiring 923 that is electrically connected tothe drain wiring 946 a, so that the pixel electrode 949 is electricallyconnected with the drain region of the current control TFT 963.

Referring next to FIG. 9(B), an organic compound layer 950, a cathode951 which is an opposing electrode and a passivation film 952 are formedby the evaporation method. It is here desired that the pixel electrode947 is heat-treated to completely remove the water content prior toforming the organic compound layer 950. In this Example, an electrodeformed of a Mg:Ag alloy is used as the cathode of the light-emittingelement, though any other material may be used, as a matter of course.

The organic compound layer 950 is formed by laminating plural layerssuch as a positive hole injection layer, a positive hole transportinglayer, an electron transporting layer, an electron injection layer and abuffer layer in addition to the light-emitting layer. The structure ofthe organic compound layer 950 used in this Example will now bedescribed in detail.

In this Example, the positive hole injection layer is formed bydepositing copper phthalocyanine, and the positive hole transportinglayer is formed by depositing MTDATA(4,4′,4′-tris(3-methylphenylphenylamino)triphenylamine) by theevaporation method. It is, however, also allowable to use a PEDOT whichis a polythiophene derivative as the positive hole injection layer, andan α-NPD or a polyphenylenevinylene (PPV) as the positive holetransporting layer.

Next, a light-emitting layer is formed. In this Example, organiccompound layers that emit different light are formed by using differentmaterials for the light-emitting layers. In this Example, organiccompound layers are formed to emit light of red, green and blue colors.

The light-emitting layer that emits light of red color is formed bydoping Alq₃ with DCM. There can be further used an Eu complex(Eu(DCM)₃(Phen)) and aluminum quinolylato complex (Alq₃) doped withDCM-1, as well as any other known material.

The light-emitting layer that emits light of green color is formed bydepositing CBP and Ir(ppy)₃ together. There can be further used analuminum quinolylato complex (Alq₃) and benzoquinolynolatoberylliumcomplex (BeBq). There can be further used the aluminum quinolylatocomplex (Alq₃) being doped with cumarin 6 or quinacridone, as well asany other known material.

As the light-emitting layer that emits light of blue color, there can beused DPVBi which is a distyryl derivative or a zinc complex having anazomethine compound as a ligand and the DPVBi doped with perylene, aswell as any other known material.

After the light-emitting layer is formed, further, there may be formedthe electron transporting layer and the electron injection layer. Inthis embodiment, a material such as 1,3,4-oxadiazole derivative or1,2,4-triazolederivative (TAZ) is used as the electron transportinglayer. Further, a buffer layer 206 may be formed by using such amaterial as lithium fluoride (LiF), aluminum oxide (Al₂O₃) orlithiumacetyl acetonate (Liacac).

The organic compound layer 950 having the laminated-layer structure mayhave a thickness of from 10 to 400 [nm] (typically, from 60 to 150[nm]), and the cathode 951 may have a thickness of from 80 to 200[nm](typically, from 100 to 150 [nm]).

After the organic compound layer 950 is formed, the cathode 951 isformed by the vaporization method to complete the light-emitting element954. In this Example, the Mg:Ag alloy is used as the electricallyconducting film that serves as the cathode 951 of the light-emittingelement 954. It is, however, also allowable to form an Al—Li alloy film(alloy film of aluminum and lithium) or a film formed by covaporizingaluminum and an element belonging to the Group 1 or the Group 2 ofperiodic table. The covaporization stands for the vaporization method bywhich the cells for being vaporized are heated together and differentsubstances are mixed together in the step of forming the film.

After the cathode 951 has been formed, a passivation film 952 is formed.Upon forming the passivation film 952, the organic compound layer 950and the cathode 951 can be protected from the water component andoxygen. In this Example, a silicon nitride film is formed maintaining athickness of 300 nm as the passivation film 952. After the cathode 951is formed, the passivation film 952 may be continuously formed withoutbeing exposed to the open air.

Thus, the light-emitting device of the structure shown in FIG. 9(C) iscompleted. A portion where the pixel electrode 949, the organic compoundlayer 950 and the cathode 951 are overlapped one upon the other,corresponds to the light-emitting element 954.

The p-channel TFT 960 and the n-channel TFT 961 are the TFTs possessedby the drive circuit, and are forming a CMOS. The switching TFT 962 andthe current control TFT 963 are the TFTs possessed by the pixel unit.The TFTs of the drive circuit and the TFTs of the pixel unit can beformed on the same substrate.

In the case of the light-emitting device using the light-emittingelement, the power source voltage of the drive circuit is about 5 toabout 6 V, and is about 10 V at the greatest. Therefore, the TFTs arenot much deteriorated by hot electrons. Further, since the drive circuitneeds to be operated at a high speed, it is desired that the gatecapacity of the TFT is better small. In the drive circuit for thelight-emitting device using light-emitting elements as in this Example,therefore, it is desired that the second impurity region 929 and thefourth impurity region 933 b possessed by the semiconductor layer of theTFT are not overlapped on the gate electrodes 918 and 919.

Thus, there is formed a light-emitting panel forming the light-emittingelements on the substrate as shown in FIG. 9(C).

The thus formed light-emitting panel is then sealed and is electricallyconnected to an external power source through an FPC to complete thelight-emitting device of the invention.

Example 2

This Example deals in detail with reference to FIG. 10 the method ofcompleting, as the light-emitting device, the light-emitting panelfabricated up to FIG. 9(C) in Example 1.

FIG. 10(A) is a top view illustrating a state where the light-emittingelement is sealed, and FIG. 10(B) is a sectional view of when FIG. 10(A)is cut along the line A-A′. A dotted line 1001 denotes a drive circuitof the source side, 1002 denotes a pixel unit, and 1003 denotes a drivecircuit of the gate side. Reference numeral 1004 denotes a coveringmember, 1005 denotes a sealing agent, and space 1007 is formed on theinside surrounded by the sealing agent 1005.

Reference numeral 1008 denotes a wiring for transmitting the signalsinput to the drive circuit 1001 of the source side and to the drivecircuit 1003 of the gate side, and video signals and clock signals arereceived through an FPC (flexible printed circuit) that serves as anexternal input terminal. Though the FPC only is diagramed here, aprinted wiring board (PWB) may be mounted on the FPC. In thisspecification, the light-emitting device includes not only thelight-emitting module of a state of mounting the FPC or the PWB on thelight-emitting panel but also the light-emitting module mounting an IC.

Next, the sectional structure will be described with reference to FIG.10(B). The pixel unit 1002 and the drive circuit 1003 on the gate sideare formed on the substrate 1000, the pixel unit 1002 being constitutedby current control TFTs 1011 and plural pixels containing transparentelectrodes 1012 electrically connected to the drains of the currentcontrol TFTs 1011. Further, the drive circuit 1003 of the gate side isconstituted by the CMOS circuit of a combination of the n-channel TFTs1013 and the p-channel TFTs 1014 (see FIG. 9).

The pixel electrode 1012 serves as the anode of the light-emittingelement. Interlayer-insulating films 1006 are formed at both ends of thepixel electrode 1012. On the pixel electrode 1012 are formed an organiccompound layer 1016 and a cathode 1017 which is an opposing electrode ofthe light-emitting element.

The cathode 1017 also works as a wiring common to plural pixels, and iselectrically connected to the FPC 1010 through the connection wiring1009. The elements included in the pixel unit 1002 and in the drivecircuit 1003 of the gate side are all covered with the passivation film1018.

The covering member 1004 is stuck with the sealing agent 1005. Theremaybe provided a spacer of a plastic film to secure a gap between thecovering member 1004 and the light-emitting element. Closed space isdefined on the inside of the sealing agent 1005, and is filled with aninert gas such as nitrogen or argon gas. A hygroscopic member asrepresented by barium oxide may be provided in the sealed space.

As the covering member 1004, there can be used a glass, ceramics,plastics or a metal. Here, however, the covering member 1004 must becapable of transmitting light when light is to be emitted on the side ofthe covering member 1004. As the plastics, there can be used FRP(fiberglass-reinforced plastics), PVF (polyvinyl fluoride), Mylar,polyester or acrylic resin.

As described above, the light-emitting panel is sealed by using thecovering member 1004 and the sealing agent 1005, in order to completelyshut the light-emitting elements off the external side and to prevent,from the external side, the infiltration of substances such as water andoxygen that deteriorate the organic compound layer upon the oxidation.It is therefore allowed to obtain a highly reliable light-emittingdevice.

This Example can be put into practice in free combination with Example1.

Example 3

FIG. 11 is a top view of the pixel unit of the light-emitting elementfabricated according to the method of Example 1. The circuitconstitution on the substrate is as shown in FIG. 11(A); i.e., there arearranged a drive circuit 1101 of the source side, a drive circuit 1102of the gate side and a pixel unit 1103.

FIG. 11(B) is a diagram illustrating, on an enlarged scale, a region a(1104) of the pixel unit 1103 in which are formed pixel electrodes(anodes in this Example) of the light-emitting elements and the organiccompound layer.

The source signal line 1105 is electrically connected to the drivecircuit 1101 of the source side. The current feeder line 1106 forsupplying the current to the light-emitting element is formed inparallel with the source signal line 1105.

Pixels 1107 formed in a plural number in the form of a matrix in thepixel unit 1103 are each surrounded by the interlayer-insulating film1108.

After the organic compound layer has been formed, a cathode 1109 whichis an opposing electrode is formed as shown in FIG. 11(C). Here,however, the source signal line 1105 and the current feeder line 1106formed on the interlayer-insulating film 1108 are located at positionshigher than the surface of the substrate as compared to the pixels 1107and, hence, the cathode 1109 is cut off. That is, the cathode 1109 iscommon to the same sequence of pixels arranged in the longitudinaldirection facing the surface of the paper, but is not common to thesequence of pixels arranged in the transverse direction.

As shown in FIG. 11(C), therefore, the connection wiring 1110 is formed.The connection wiring 1110 has been formed already simultaneously withthe electrode wiring and the gate electrode. Upon electricallyconnecting the cathode 1109 which serves as a wiring common to pluralpixels to the connection wiring 1110 on the interlayer-insulating film1108 through the connection portion shown in FIG. 11(C), therefore, allpixels are connected to the external power source. The connection wiring1110 may be formed at the lower portion of the pixel unit facing thesurface of the paper as shown in FIG. 11(C) or may be formed in theupper portion. Or, the connection wirings 1110 may be formed at theupper and lower portions. These structures help prevent linear defectcaused by the breakage of the cathode 1109 shared by the sequence ofpixels. This Example can be put into practice in free combination withthe constitution of Example 1 or Example 2.

Example 4

An external light emitting quantum efficiency can be remarkably improvedby using an organic material (which is also referred to as tripletcompounds) by which phosphorescence from a triplet exciton can beemployed for emitting a light. As a result, the power consumption of thelight-emitting element can be reduced, the lifetime of thelight-emitting element can be elongated and the weight of thelight-emitting element can be lightened.

The following is a report where the external light emitting quantumefficiency is improved by using the triplet exciton (T. Tsutsui, C.Adachi, S. Saito, Photochemical processes in Organized MolecularSystems, ed. K. Honda, (Elsevier Sci. Pub., Tokyo, 1991) p. 437).

The molecular formula of an organic material (coumarin pigment) reportedby the above article is represented as follows.

(M. A. Baldo, D.F.O' Brien, Y. You, A. Shoustikov, S. Sibley, M. E.Thompson, S. R. Forrest, Nature 395 (1998) p.151)

The molecular formula of an organic material (Pt complex) reported bythe above article is represented as follows.

(M. A. Baldo, S. Lamansky, P. E. Burrows, M. E. Thompson, S. R. Forrest,Appl. Phys. Lett., 75 (1999) p.4.)(T. Tsutsui, M. -J. Yang, M. Yahiro, K. Nakamura, T. Watanabe, T. Tsuji,Y. Fukuda, T. Wakimoto, S. Mayaguchi, Jpn, Appl. Phys., 38 (12B) (1999)L1502)

The molecular formula of an organic material (Ir complex) reported bythe above article is represented as follows.

As described above, if phosphorescence from a triplet exciton can be putto practical use, it can realize the external light emitting quantumefficiency three to four times as high as that in the case of usingfluorescence from a singlet exciton in principle.

Further, it is possible that the organic material of this embodiment isused to the organic compound layer of the light-emitting device shown inEmbodiments 1 to 3.

Example 5

The light-emitting device fabricated in accordance with the presentinvention is of the self-emission type, and thus exhibits more excellentrecognizability of the displayed image in a light place as compared tothe liquid crystal display device. Furthermore, the light-emittingdevice has a wider viewing angle. Accordingly, various electronicdevices can be completed by using the light-emitting device of thepresent invention to a display portion.

Such electronic devices include a video camera, a digital camera, agoggles-type display (head mount display), a navigation system, a soundreproduction device (a car audio equipment and an audio set), a laptoppersonal computer, a game machine, a portable information terminal (amobile computer, a portable telephone, a portable game machine, anelectronic book, or the like), an image reproduction apparatus includinga recording medium (more specifically, an apparatus which can reproducea recording medium such as a digital video disc (DVD) and so forth, andincludes a display for displaying the reproduced image), or the like. Inparticular, in the case of the portable information terminal, use of theself-emission device is preferable, since the portable informationterminal that is likely to be viewed from a tilted direction is oftenrequired to have a wide viewing angle. FIG. 12 respectively showsvarious specific examples of such electronic devices.

FIG. 12A illustrates a display device which includes a frame 2001, asupport table 2002, a display portion 2003, a speaker portion 2004, avideo input terminal 2005 or the like. The display device can becompleted by using the light-emitting device manufactured by the presentinvention to the display portion 2003. The light-emitting device is ofthe self-emission type and therefore requires no back light. Thus, thedisplay portion thereof can have a thickness thinner than that of theliquid crystal display device. The display device is including all ofthe display device for displaying information, such as a personalcomputer, a receiver of TV broadcasting and an advertising display.

FIG. 12B illustrated a digital still camera which includes a main body2101, a display portion 2102, an image receiving portion 2103, anoperation key 2104, an external connection port 2105, a shutter 2106, orthe like. The digital still camera manufactured by the present inventioncan be completed by using the light-emitting device to the displayportion 2102.

FIG. 12C illustrates a laptop type personal computer which includes amain body 2201, a casing 2202, a display portion 2203, a keyboard 2204,an external connection port 2205, a pointing mouse 2206, or the like.The laptop type personal computer can be completed by using thelight-emitting device manufactured by the present invention to thedisplay portion 2203.

FIG. 12D illustrated a mobile computer which includes a main body 2301,a display portion 2302, a switch 2303, an operation key 2304, aninfrared port 2305, or the like. The mobile computer can be completed byusing the light-emitting device to the display portion 2302.

FIG. 12E illustrates an image reproduction apparatus including arecording medium (more specifically, a DVD reproduction apparatus),which includes a main body 2401, a casing 2402, a display portion A2403, another display portion B 2404, a recording medium (DVD or thelike) reading portion 2405, an operation key 2406, a speaker portion2407 or the like. The display portion A 2403 is used mainly fordisplaying image information, while the display portion B 2404 is usedmainly for displaying character information. The image reproductionapparatus can be completed by using the light-emitting devicemanufactured by the present invention to the display portion A 2403 andB 2404. The image reproduction apparatus including a recording mediumfurther includes a game machine or the like.

FIG. 12F illustrates a goggle type display (head mounted display) whichincludes a main body 2501, a display portion 2502, an arm portion 2503.The light-emitting device in accordance with the present invention canbe used as the display portion 2502.

FIG. 12G illustrates a video camera which includes a main body 2601, adisplay portion 2602, an audio input portion 2603, an externalconnecting port 2604, a remote control receiving portion 2605, an imagereceiving portion 2606, a battery 2607, a sound input portion 2608, anoperation key 2609, or the like. The video camera can be completed byusing the light-emitting device manufactured by the present invention tothe display portion 2602.

FIG. 12H illustrates a mobile phone which includes a main body 2701, acasing 2702, a display portion 2703, a sound input portion 2704, a soundoutput portion 2705, an operation key 2706, an external connecting port2707, an antenna 2708, or the like. The mobile phone can be completed byusing the light-emitting device manufactured by the present invention tothe display portion 2703. Note that the display portion 2703 can reducepower consumption of the portable telephone by displaying white-coloredcharacters on a black-colored background.

When the brighter luminance of the organic material becomes available inthe future, the light-emitting device in accordance with the presentinvention will be applicable to a front-type or rear-type projector inwhich light including output image information is enlarged by means oflenses or the like to be projected.

The aforementioned electronic devices are more likely to be used fordisplay information distributed through a telecommunication path such asInternet, a CATV (cable television system), and in particular likely todisplay moving picture information. The light-emitting device issuitable for displaying moving pictures since the organic material canexhibit high response speed.

A portion of the light-emitting device that is emitting light consumespower, so it is desirable to display information in such a manner thatthe light-emitting portion therein becomes as small as possible.Accordingly, when the light-emitting device is applied to a displayportion which mainly displays character information, e.g., a displayportion of a portable information terminal, and more particular, aportable telephone or a sound reproduction device, it is desirable todrive the light-emitting device so that the character information isformed by a light-emitting portion while a non-emission portioncorresponds to the background.

As set forth above, the light-emitting device formed by using thepresent invention can be applied variously to a wide range of electronicdevices in all fields. The electronic device in the present embodimentcan be completed by using a light-emitting device shown in Embodiments 1through 3 to the display portion.

According to this invention as described above, a function is impartedby utilizing the shape of the wiring to substitute for the bank that hasheretofore been formed by using a mask. Further, the shape of the wiringhelps solve the problem of short-circuit between the wiring and theopposing electrode. The invention, therefore, makes it possible tosimplify the process for producing the light-emitting device and toproduce the devices maintaining a throughput higher than ever before.

1-81. (canceled)
 82. A display device comprising: a TFT over a substrate; a light-emitting element over the substrate, the light-emitting element comprising a first electrode, a light-emitting layer and a second electrode; a first wiring electrically connected to the first electrode; an insulating film provided over the first wiring; and a second wiring provided over the first wiring and over the insulating film, wherein the second wiring is electrically connected to the TFT and the first wiring.
 83. A display device according to claim 82, wherein the light-emitting layer comprises an organic compound layer.
 84. A display device according to claim 82, wherein the TFT is a current control TFT.
 85. A display device according to claim 82, wherein the TFT comprises a source region, a drain region and a channel region.
 86. An electronic apparatus having the display device according to claim
 82. 87. An electronic apparatus according to claim 86, wherein the electronic apparatus is selected from the group consisting of a digital camera, a notebook-type personal computer, a mobile computer, a portable image-reproducing device equipped with a recording medium, a goggle-type display, a video camera, a portable telephone, a navigation system, a sound reproduction device and a game machine.
 88. A display device comprising: a TFT over a substrate; a light-emitting element over the substrate, the light-emitting element comprising a first electrode, a light-emitting layer and a second electrode; a first wiring electrically connected to the first electrode; an insulating film provided over the first wiring; a second wiring provided over the first wiring and over the insulating film, wherein the second wiring is electrically connected to the TFT and the first wiring; and a separation portion provided over the second wiring.
 89. A display device according to claim 88, wherein the light-emitting layer comprises an organic compound layer.
 90. An electronic apparatus having the display device according to claim
 88. 91. An electronic apparatus according to claim 90, wherein the electronic apparatus is selected from the group consisting of a digital camera, a notebook-type personal computer, a mobile computer, a portable image-reproducing device equipped with a recording medium, a goggle-type display, a video camera, a portable telephone, a navigation system, a sound reproduction device and a game machine.
 92. A display device according to claim 88, wherein the separation portion comprises a material that provides an etching rate smaller than that of a material forming the second wiring with respect to an etching solution selected from the group consisting of a hydrofluoric acid, a mixed solution containing a hydrofluoric acid, and a mixed solution of phosphoric acid, nitric acid and acetic acid.
 93. A display device according to claim 88, wherein the separation portion comprises a material selected from the group consisting of an inorganic material, a metal and an organic resin.
 94. A display device according to claim 88, wherein the TFT is a current control TFT.
 95. A display device according to claim 88, wherein the TFT comprises a source region, a drain region and a channel region.
 96. A method of fabricating a display device comprising: forming a source region, a drain region and a channel region over a substrate; forming a gate insulating film over the source region, the drain region and the channel region; forming a gate electrode and a first wiring; forming an insulating film over the gate electrode and over the first wiring; removing part of the insulating film formed over the first wiring; forming a second wiring over the first wiring and over the insulating film, wherein the second wiring is electrically connected to one of the source region and the drain region; forming a separation portion over the second wiring; and forming a light-emitting element electrically connected to the first wiring.
 97. A method of fabricating a display device according to claim 96, wherein the display device is incorporated into an electronic apparatus selected from the group consisting of a digital camera, a notebook-type personal computer, a mobile computer, a portable image-reproducing device equipped with a recording medium, a goggle-type display, a video camera, a portable telephone, a navigation system, a sound reproduction device and a game machine.
 98. A method of fabricating a display device according to claim 96, wherein the separation portion comprises a material that provides an etching rate smaller than that of a material forming the second wiring with respect to an etching solution selected from the group consisting of a hydrofluoric acid, a mixed solution containing a hydrofluoric acid, and a mixed solution of phosphoric acid, nitric acid and acetic acid.
 99. A method of fabricating a display device according to claim 96, wherein the separation portion comprises a material selected from the group consisting of an inorganic material, a metal and an organic resin.
 100. A method of fabricating a display device comprising: forming a source region, a drain region and a channel region over a substrate; forming a gate insulating film over the source region, the drain region and the channel region; forming a gate electrode and a first wiring; forming an insulating film over the gate electrode and over the first wiring; removing part of the insulating film formed over the first wiring; forming a second wiring over the first wiring and over the insulating film, wherein the second wiring is electrically connected to one of the source region and the drain region; forming a separation portion over the second wiring; and forming a first electrode, a light-emitting layer and a second electrode of a light-emitting element by using the separation portion as a mask.
 101. A method of fabricating a display device according to claim 100, wherein the display device is incorporated into an electronic apparatus selected from the group consisting of a digital camera, a notebook-type personal computer, a mobile computer, a portable image-reproducing device equipped with a recording medium, a goggle-type display, a video camera, a portable telephone, a navigation system, a sound reproduction device and a game machine.
 102. A method of fabricating a display device according to claim 100, wherein the separation portion comprises a material that provides an etching rate smaller than that of a material forming the second wiring with respect to an etching solution selected from the group consisting of a hydrofluoric acid, a mixed solution containing a hydrofluoric acid, and a mixed solution of phosphoric acid, nitric acid and acetic acid.
 103. A method of fabricating a display device according to claim 100, wherein the separation portion comprises a material selected from the group consisting of an inorganic material, a metal and an organic resin.
 104. A method of fabricating a display device according to claim 100, wherein the first electrode is formed in contact with the first wiring.
 105. A method of fabricating a display device comprising: forming a source region, a drain region and a channel region over a substrate; forming a gate insulating film over the source region, the drain region and the channel region; forming a gate electrode and a first wiring; forming a first insulating film over the gate electrode and over the first wiring; removing part of the first insulating film formed over the first wiring; forming a second wiring over the first wiring and over the first insulating film, wherein the second wiring is electrically connected to one of the source region and the drain region; forming a second insulating film over the second wiring; and forming a partitioning wall by etching the second wiring and the second insulating film.
 106. A method of fabricating a display device according to claim 105, wherein the display device is incorporated into an electronic apparatus selected from the group consisting of a digital camera, a notebook-type personal computer, a mobile computer, a portable image-reproducing device equipped with a recording medium, a goggle-type display, a video camera, a portable telephone, a navigation system, a sound reproduction device and a game machine.
 107. A method of fabricating a display device according to claim 105, wherein the second insulating film comprises a material that provides an etching rate smaller than that of a material forming the second wiring with respect to an etching solution selected from the group consisting of a hydrofluoric acid, a mixed solution containing a hydrofluoric acid, and a mixed solution of phosphoric acid, nitric acid and acetic acid.
 108. A method of fabricating a display device according to claim 105, wherein the second insulating film comprises a material selected from the group consisting of an inorganic material, a metal and an organic resin. 